Access portals provide a convenient method to repeatedly deliver medicants to remote areas of the body without utilizing surgical procedures. Portals are totally implantable within the body, i.e. subcutaneous, and permit the infusion of medicants, parenteral solutions, blood products, and other fluids. Portals may also be used for blood sampling.
A typical portal generally includes a housing assembly, a septum, and an outlet. The housing assembly and septum define a reservoir which is accessible through the septum. The outlet includes or is attached to a catheter which accesses a vein. The catheter delivers fluid from the portal to a remote location in the body, for example the superior vena cava. The outlet may be an integral catheter as in U.S. Pat. No. 4,471,885 to Weeks, or a separate metallic outlet tube assembly as in U.S. Pat. No. 5,213,574 to Tucker. In the case of a portal with an outlet tube assembly, a catheter will be attached thereto.
In common practice, the portal is implanted within the body and the catheter is routed to a remote area were fluid is desired to be delivered. To deliver the fluid, a caregiver locates the septum of the portal by palpation of the patient's skin. Portal access is accomplished by percutaneously inserting a needle, typically a non-coring needle, perpendicularly through the septum of the portal and into the reservoir. The drug or medicant is then administered by bolus injection or continuous infusion. Ordinarily, the fluid flows through the reservoir into the catheter and finally to the site were the fluid is desired.
Portals generally come in two different types, surgical and cosmetic. Surgical portals are used to deliver medicants, including chemotherapy drugs which may be harmful to surrounding tissue, as well as sampling blood. Cosmetic portals, on the other hand, are utilized to deliver saline or some other non-reactive substance to a prosthesis which supplements a body feature. An example of a surgical portal is shown in U.S. Pat. No. 5,213,574, while an example of a cosmetic portal is shown in U.S. Pat. No. 4,471,885.
A concern for all portals, and especially portals used for surgical procedures, is blowout. Blowout describes the catastrophic failure of a portal when the pressure inside the reservoir is great enough to disengage the septum from the housing of the portal. Disengagement of the septum may injure the patient, and release medication contained in the portal. The released medicant will often be harmful to the surrounding tissue. Blowouts have a variety of causes. For example, a blowout may be caused if the catheter downstream of the portal is occluded and a bolus injection is attempted. When the bolus injection is attempted the injected fluid cannot travel through the catheter and as fluid is continually injected into the reservoir of the portal the pressure increases until the septum is disengaged.
Blowouts are of a much greater concern for surgical portals than for cosmetic portals. A primary reason for this is that the reservoirs of surgical portals often contain caustic medicants while the reservoirs of cosmetic portals do not. To prevent blowout, surgical portals typically hold the septum in the housing of the portal under great compression. For example, the SIMS Deltec PORT-A-CATH brand portal uses an interference fit to both radially and axially compress the septum to hold it in place.
In contrast, some cosmetic portals, for example, the portal shown in U.S. Pat. No. 4,371,885, are sealed to the housing by compressing only a preformed ridge around the septum with, for example, a threaded ring. The threaded ring of U.S. Pat. No. 4,371,885 does not provide as much compressive force as the PORT-A-CATH portal.
Another concern with portals, and more importantly with surgical portals, is puncture life. Puncture life describes the number of punctures a septum can resist and still provide a fluid tight seal. If the septum does not reseal after an injection is made, the injected medicant may leak out of the reservoir and possibly harm the surrounding tissue. Once again, septum life is of greater importance in surgical portals than cosmetic portals because of the nature of the medicant being injected. Commercially successful prior art surgical portals have also utilized a compressed septum to increase puncture life.
Typical portals are manufactured with preformed or discrete septums. The portal is assembled by inserting the septum into the housing and then compressing the septum. The septum can be compressed either with separate components or by "shoehorning" a larger septum into a housing having an aperture with a smaller diameter. An example of a portal with a "shoehorned" septum is shown in U.S. Pat. No. 5,045,060 to Melsky et al. A disadvantage of any portal having a preformed septum is increased cost of manufacture. The increased cost is caused, in part, by the fact that the components used to seal the septum require precise tolerances in their dimensions.
Another concern with preformed septums compressively sealed against the portal is a decrease in the target area, provided by the septum, to the caregiver. The target area describes the exposed portion of the septum, through which a needle can access the reservoir. Some prior art portals have attempted to increase the "target area" of the septum available to the caregiver without much success. For example, some of these prior art devices have attempted to increase the target area by providing integrally molded elastomeric domes accessible from a plurality of directions. However, the integrally molded domes of the prior art have at least two significant problems. The first problem is that the caregiver is never completely sure when the needle is in the reservoir. For example, the caregiver may push the needle through a side wall and out into the body cavity, believing the needle to be in the reservoir. Second, when pushing the needle into the reservoir the elastomeric dome may collapse, thereby inhibiting injection of any medicant into the reservoir.
Solutions to the problems with domed portals have been proposed by the prior art. An example is an OMEGAPORT brand portal manufactured by Norfolk Medical of Skokie, Ill. The OMEGAPORT brand portal includes an elastomeric dome which is reinforced by an internal wire cage. The wire cage solves the problem of the dome collapsing upon insertion of the needle, but provides no indication to the caregiver of when the needle is in the reservoir. Further, the wire cage presents its own problems. These problems include needles deflecting off of the cage and away from the reservoir.
Therefore, a need has arisen to provide a portal and a method of manufacture which effectively increases the target area of the portal, yet achieves all of the benefits of traditional portals which utilize compressed septums. Additionally there is a need to decrease the cost of manufacturing portals, including making portals easier to manufacture. The portal of the present invention solves these and other problems of the prior art.